Evaporatively cooled heat exchanger

ABSTRACT

An heat exchanger assembly includes a plurality of tubes defining a plurality of parallel refrigerant passages therein carrying a refrigerant longitudinally from an inlet header to an outlet header. Water flows from a reservoir through a distributor apparatus to provide even wetting between the ends of the tubes as the water flows laterally over the tubes between an entry edge and an exit edge. A screen is provided adjacent the exit edge to collect excess water to be deposited into a water tray provided beneath and spaced from the exit edge of the tubes. A pump is provided to move water from the water tray to the reservoir to preserve water. If excess water is lost, such as through evaporation, a supplemental water feed line provides supplemental water to the system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention relates to a heat exchanger assembly.

2. Description of the Prior Art

Conventional vapor compression air conditioning systems include an evaporator for transferring heat from ambient air to evaporate a refrigerant, a compressor for compressing the refrigerant into a superheated vapor, and a condenser to condense the refrigerant back to a subcooled liquid so that it can be provided back to the evaporator through an expansion device. Known condenser assemblies include a plurality of tubes extending longitudinally between an inlet end and an outlet end for carrying a refrigerant flowing between an inlet header and an outlet header. Most condenser assemblies are cooled by ambient air flowing on the outside of the tubes. Since the heat removal capacity of air is low, attempts have been made to improve the heat removal efficiency of the condenser by using liquid water as the cooling medium in conjunction with air. This improves the heat transfer rate considerably due to latent heat of evaporation of liquid water.

One such heat exchanger is disclosed in WO 00/68628 to Phelps et al., which shows a hose connected to a water outlet that drips water over condenser fins. A controller is responsive to a sensed air temperature to shut off the water flow below a certain air temperature. The system is optimized by visually inspecting the condenser to see if there is excess or insufficient water near the bottom of the unit. However, there is no mechanism to ensure that the water uniformly wets the condenser surface.

A similar heat exchanger is shown in U.S. Pat. No. 4,672,817 to Croce, which shows a condenser having a perforated copper tube to allow water to saturate a wicking material until it drips vertically down over an array of fins. A common disadvantage of the condensers of Croce and Phelps is that the water flows over the fins.

SUMMARY OF THE INVENTION AND ADVANTAGES

The invention provides for such a heat exchanger including a distributor apparatus for distributing water between the ends of the tubes to flow laterally across the tubes from the entry edge to the exit edge.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a schematic view of a heat exchanger in accordance with a first embodiment of the present invention;

FIG. 2 is a schematic view of a heat exchanger in accordance with a second embodiment of the present invention;

FIG. 3 is a perspective view of a heat exchanger in accordance with either embodiment of the present invention;

FIG. 4 is a cross sectional view of a heat exchanger according to an aspect of the present invention;

FIG. 5 is a cross sectional view of a heat exchanger according to a second aspect of the present invention;

FIG. 6 is a perspective view of a heat exchanger tube according to a third aspect of the present invention;

FIG. 7 is a perspective view of a heat exchanger tube according to a fourth aspect of the present invention;

FIG. 8 is a perspective view of a heat exchanger tube according to a fifth aspect of the present invention;

FIG. 9 is a flow chart showing the control logic for an electronic control according to the first exemplary embodiment of the present invention; and

FIG. 10 is a flow chart showing the control logic for an electronic control according to the second exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a heat exchanger assembly 20 is generally indicated including a plurality of tubes 22 extending longitudinally between an inlet end and an outlet end, and a extending between a pair of headers 24, 26. Referring generally to FIGS. 1-3, an inlet header 24 is in fluid communication with the inlet end of the tubes 22 for supplying a refrigerant to the tubes 22, and an outlet header 26 is in fluid communication with the outlet end of the tubes 22 for receiving the refrigerant. Each of the tubes 22 has a cross section including a pair of sides extending laterally between an entry edge and an exit edge. A plurality of dividers 28 extend longitudinally between the ends and between the sides to define a plurality of parallel refrigerant passages extending within each tube 22. The headers 24, 26 extend vertically between a bottom and a top and the tubes 22 extend horizontally between the headers 24, 26 such that the sides of adjacent tubes 22 face one another. The tubes 22 are vertically spaced from one another between a bottom tube 30 extending adjacent the bottoms of the headers 24, 26 and a top tube 32 extending adjacent the tops of the headers 24, 26.

Referring again to FIGS. 1 and 2, according to the exemplary embodiments, the tubes 22 receive superheated refrigerant from the inlet header 24 and provide subcooled refrigerant to the outlet header 26. A blower 34 is provided immediately upstream from the entry edge of the tubes 22 to move air over the sides of the tubes 22 to cool the refrigerant. The entry edge of the tubes 22 is disposed immediately downstream of the blower 34, and the exit edge is disposed remotely downstream from the blower 34. A watering system provides a supply of water to wet each of the tubes 22. The watering system includes a reservoir 36 for storing the supply of water, and a wicking coating extending along the sides of the tubes 22 for wicking water uniformly over the sides of the tubes 22. Heat from the refrigerant evaporates the water into vapor, and the vapor is carried away by the blower 34. A distributor apparatus distributes water between the ends of the tubes 22 to flow laterally across the tubes 22 from the entry edge to the exit edge. The distributor apparatus includes a pipe 38 leading from the reservoir 36 to a plurality of branches 40, with each branch 40 leading to one of a plurality of manifolds 42 extending along the entry edges of each tube 22.

A screen 44 is provided adjacent the exit edge of the tubes 22 for collecting excess water flowing from each tube 22, and a water tray 46 is provided below the screen 44 and spaced from the exit edge of the tubes 22 for receiving the excess water from the screen 44 and from the tubes 22. A pump 48 is provided to move water from the water tray 46 to the reservoir 36, and an electronic control 50 in communication with the pump 48 and the water tray 46 activates the pump 48 according to the volume of water in the water tray 46. To accomplish this, the electronic control 50 includes a high level water tray sensor 52 positioned within the water tray 46 to activate the pump 48 in response to a high level of water in the water tray 46.

According to a first exemplary embodiment, shown specifically in FIG. 1, a supplemental water feed line 54 is provided to supply water from a supplemental source, such as a city water line, to the water tray 46. A supplemental valve 56 within the supplemental water feed line 54 is in communication with the electronic control 50, which includes a low level water tray sensor 58 and a low level reservoir sensor 60. If the water level in both the water tray 46 and the reservoir 36 falls below a threshold value, the supplemental valve 56 is opened to allow water to flow from the supplemental source into the water tray 46, as shown by the control logic of FIG. 9. The controller reads the level of the water tray 46, represented as L₁, and the level of the reservoir 36, represented as L_(h) and compares the levels first to a desired setting in each respective container, represented as L_(s1) and L_(sh), respectively. If the sum of the levels of the water tray 46 and reservoir 36 is less than the sum of the respective desired settings, the supplemental valve 56 is opened. Additionally, the level of the water tray 46 is compared to the desired setting for the water tray 46. If L₁ is greater than L_(s1), pump 48 is activated to move water into the reservoir 36. The pump 48 will stop when L_(h) is greater than L_(sh), or will alternatively stop when L₁ is less than L_(s1).

According to a second exemplary embodiment, shown specifically in FIG. 2, the supplemental water feed line 54 supplies water from the supplemental source directly into the reservoir 36. The electronic control 50 communicates with the low level reservoir sensor 60 to activate the supplemental valve 56 in response to a low level of water in the reservoir 36. If the water level in the reservoir 36 falls below a threshold value, the supplemental valve 56 is opened to allow water to flow from the supplemental source to the reservoir 36, as shown in the control logic of FIG. 10. In this embodiment, only a water tray 46 sensor is used, represented again as L₁, and desired setting for the water tray 46 is represented as L_(s1). When L₁ is less than L_(s1), the pump 48 will be stopped to prevent pumping all of the water out of the water tray 46, and the supplemental valve 56 will be opened to refill the water tray 46. Once L₁ becomes greater than L_(s1), the pump 48 will be reactivated to fill the reservoir 36, and the supplemental valve 56 will be closed.

The water metering system distributes a specified flow rate of water from the reservoir 36 to the sides of the tubes 22. According to the first exemplary embodiment shown in FIG. 1, the water metering system includes a metering valve 62 in the pipe 38 for adjustably controlling the flow rate of water from the reservoir 36 to the tubes 22. The metering valve 62 of the present embodiment is a solenoid valve in communication with the electronic control 50. The reservoir 36 of the present embodiment is positioned vertically above the top tube 32 so that gravity will draw the water from the reservoir 36 toward the tubes 22 when the metering valve 62 is opened. To initiate water flow from the reservoir 36, a high level reservoir sensor 64 communicates with the electronic control 50 to activate the solenoid valve in response to a high level of water in the reservoir 36. Once the valve has been opened, it remains open as long as the heat exchanger is operating so that the water flow is continuous.

According to the second exemplary embodiment shown in FIG. 2, the reservoir 36 is positioned below or level with the tubes 22 of the heat exchanger. The water metering system includes a wicking material to draw water by capillary action from the reservoir 36 to the manifolds 42.

According to a first aspect of either embodiment, as shown in FIGS. 1 and 2, the sides of the tubes 22 slope downwardly from the entry edge to the exit edge. Each of the sides of the tubes 22 slope at the same angle so that the sides of the tubes 22 are parallel with each other. Alternatively, as shown in FIG. 4, the sides of the bottom tube 30 slope at a first angle and the sides of the top tube 32 slope at a last angle different from the first angle. Each tube 22 between the bottom tube 30 and the top tube 32 slopes at progressively increasing angles from the first angle to the last angle to promote more efficient wetting of the plurality of tubes 22.

According to a second aspect of either embodiment, as show in FIG. 5, the bottom tube 30 has a first distance between the entry edge and the exit edge and the top tube 32 has a last distance between the entry edge and the exit edge. The last distance is greater than the first distance and each of the tubes 22 between the bottom and top tubes 30, 32 have a progressively increasing distance between the entry edge and the exit edge from the first distance and less than the last distance. The varying distances allows the heat exchanger to be customized according to the local cooling load.

According to a third aspect of either embodiment, as shown in FIG. 6, the sides of the tubes 22 have a profile having a flat shape between the ends. According to a fourth aspect, as shown in FIG. 7, the sides of the tubes 22 have a profile having an arced shape between the ends. According to a fifth aspect, as shown in FIG. 8, the sides of the tubes 22 have a profile having a ridged semi-circular shape extending between the entry and exit edges, the profile formed as a result of extruding the tubes 22 so that the refrigerant passages have a circular shape integrally formed with one another.

While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 

1. A heat exchanger assembly comprising; a plurality of tubes extending longitudinally between an inlet end and an outlet end for carrying a refrigerant between said ends, each of said tubes having a cross section including a pair of sides extending laterally between an entry edge and an exit edge, an inlet header in fluid communication with said inlet end of said tubes for supplying refrigerant to said passages in said tubes, an outlet header in fluid communication with said outlet end of said tubes for receiving the refrigerant from said passages in said tubes, a watering system for providing a supply of water to wet each of said tubes, said watering system including a reservoir for storing the supply of water, and said watering system including a distributor apparatus for distributing water between said ends of said tubes to flow laterally across said tubes from said entry edge to said exit edge.
 2. A heat exchanger assembly as set forth in claim 1 wherein said distributor apparatus includes a plurality of manifolds with each manifold extending along a different one of said entry edges of said tubes for distributing water at said entry edges.
 3. A heat exchanger assembly as set forth in claim 2 wherein said watering system includes a plurality of branches in fluid communication with said reservoir and said manifolds with each branch supplying water to a different one of said manifolds.
 4. A heat exchanger assembly as set forth in claim 3 wherein said headers extend vertically between a bottom and a top and said tubes extend horizontally between said headers with said sides of adjacent tubes facing one another and vertically spaced from one another between a bottom tube extending adjacent said bottoms of said headers and a top tube extending adjacent said tops of said headers.
 5. A heat exchanger assembly as set forth in claim 4 wherein said sides of said tubes slope downwardly from said entry edge to said exit edge.
 6. A heat exchanger assembly as set forth in claim 5 wherein each of said sides of said tubes slope at the same angle to extend parallel with each other.
 7. A heat exchanger assembly as set forth in claim 5 wherein said sides of said bottom tube slope at a first angle and said sides of said top tube slope at a last angle different from said first angle and each tube between said bottom tube and said top tube slopes at progressively increasing angles from said first angle to said last angle.
 8. A heat exchanger assembly as set forth in claim 4 wherein said bottom tube has a first distance between said entry edge and said exit edge and said top tube has a last distance between said entry edge and said exit edge and wherein said last distance is greater than said first distance and wherein each of said tubes between said bottom and top tubes have a progressively increasing distance between said entry edge and said exit edge from said first distance and less than said last distance.
 9. A heat exchanger assembly as set forth in claim 4 including a water tray spaced from said exit edges of said tubes for receiving excess water exiting from each tube.
 10. A heat exchanger assembly as set forth in claim 9 further comprising a screen positioned adjacent said exit edge of said tubes for collecting excess water flowing from each tube and for delivering the excess water into said water tray.
 11. A heat exchanger assembly as set forth in claim 9 including a pump for moving water from said water tray to said reservoir.
 12. A heat exchanger assembly as set forth in claim 11 including an electronic control in communication with said pump and said water tray for activating said pump in response to the volume of water in said water tray.
 13. A heat exchanger assembly as set forth in claim 12 wherein said electronic control includes a high level water tray sensor for activating said pump in response to a high level of water in said water tray.
 14. A heat exchanger assembly as set forth in claim 13 including a supplemental water feed line for selectively supplying water from a supplemental source to said water tray and a supplemental valve in said supplemental water feed line in communication with said electronic control and said electronic control including a low level water tray sensor and a low level reservoir sensor for activating said supplemental valve in response to a low level of water in said water tray and in said reservoir.
 15. A heat exchanger assembly as set forth in claim 13 including a supplemental water feed line for selectively supplying water from a supplemental source to said reservoir and a supplemental valve in said supplemental water feed line in communication with said electronic control and said electronic control including a low level reservoir sensor for activating said supplemental valve in response to a low level of water in said reservoir.
 16. A heat exchanger assembly as set forth in claim 12 further comprising a water metering system for distributing a specified flow rate of water from said reservoir to said sides of said tubes.
 17. A heat exchanger assembly as set forth in claim 16 wherein said water metering system includes a wicking material for drawing water by capillary action from said reservoir to said manifolds.
 18. A heat exchanger assembly as set forth in claim 16 wherein said water metering system includes a metering valve between said reservoir and said branches for adjustably controlling the flow rate of water from said reservoir to said tubes.
 19. A heat exchanger assembly as set forth in claim 18 wherein said metering valve comprises a solenoid valve in communication with said electronic control.
 20. A heat exchanger assembly as set forth in claim 19 wherein said electronic control includes a high level reservoir sensor for activating said solenoid valve in response to a high level of water in said reservoir.
 21. A heat exchanger assembly as set forth in claim 4 wherein said sides of said tubes have a profile having a flat shape between said ends.
 22. A heat exchanger assembly as set forth in claim 4 wherein said sides of said tubes have a profile having an arced shape between said ends.
 23. A heat exchanger assembly as set forth in claim 4 wherein said sides of said tubes have a profile having a ridged semi-circular shape extending between said entry and exit edges.
 24. A heat exchanger assembly as set forth in claim 4 including a wicking coating extending along said sides of said tubes for wicking water uniformly over said sides of said tubes.
 25. A heat exchanger assembly as set forth in claim 4 further comprising a blower for moving air over said sides of said tubes.
 26. A heat exchanger assembly as set forth in claim 25 further comprising said entry edge of said tubes disposed immediately downstream of said blower and said exit edge of said tubes disposed remotely downstream from said blower.
 27. A heat exchanger assembly comprising; a plurality of tubes extending longitudinally between an inlet end and an outlet end for carrying a refrigerant longitudinally between said ends, each of said tubes having a cross section including a pair of sides extending laterally between an entry edge and an exit edge and including dividers extending longitudinally between said ends and between said sides to define a plurality of parallel refrigerant passages, an inlet header in fluid communication with said inlet end of said tubes for supplying the refrigerant to said passages in said tubes, an outlet header in fluid communication with said outlet end of said tubes for receiving the refrigerant from said passages in said tubes, said headers extending vertically between a bottom and a top and said tubes extending horizontally between said headers with said sides of adjacent tubes facing one another and vertically spaced from one another between a bottom tube extending adjacent said bottoms of said headers and a top tube extending adjacent said tops of said headers, a blower for moving air over said sides of said tubes, said entry edge of said tubes disposed immediately downstream of said blower and said exit edge of said tubes disposed remotely downstream from said blower, a watering system for providing a supply of water to wet each of said tubes, said watering system including a reservoir for storing the supply of water, a wicking coating extending along said sides of said tubes for wicking water uniformly over said sides of said tubes, said watering system including a distributor apparatus for distributing water between said ends of said tubes to flow laterally across said tubes from said entry edge to said exit edge, said distributor apparatus including a plurality of manifolds extending along said entry edges of each tube in fluid communication with said reservoir, said watering system including a pipe in fluid communication with said reservoir and a plurality of branches in fluid communication with said pipe with each branch supplying water to said entry edge of a different one of said tubes, a screen positioned adjacent said exit edge of said tubes for collecting excess water flowing from each tube, a water tray positioned below said screen and spaced from said exit edge of said tubes for receiving the excess water therefrom, a pump for moving water from said water tray to said reservoir, an electronic control in communication with said pump and said water tray for activating said pump in response to the volume of water in said water tray, and a water metering system for distributing a specified flow rate of water from said reservoir to said sides of said tubes. 